Patio sub base.

[Jay1111]

Good evening all,

Pictured below is my current decking area having removed the rotted top boards and soon to remove the frame seen. Below this are 4 block dwarf block walls supporting the timbers above.

I am planning to replace the decking with something more substantial such as slate paving.

My question is, just how deep can a compacted sub base be? Is it possible for me to fill between the dwarf walls with MOT1 aggregate (would be approx 150mm deep) , compact that down, then put a screed on that and lay slabs. Or do the channels between the dwarf walls need filling with concrete?

Any and all help appreciated!

 

[John D v2.0]

Whacking down type 1 mot is always going to be much cheaper and cleaner than mixing concrete for any significant area. Hiring the mixer is a bit cheaper than a whacker and the aggregate is similar cost but at 5 pounds a bag the cement is the not so hidden cost there.
You can't whack down 150mm in total but make sure you do it as a thinner layer maybe 70mm and then do the rest after that's whacked down well
Then you can mix up a lean dryish 8:1 sharp and mix for laying your slabs on top.
Good luck!

 

[Jay1111]

Great thats what I needed to know!

Presumably once my whacked in layers of MOT meets the top of my existing block walls, I can lay the screed and slabs into that flat area, which would consist partly of solid block and partly whacked MOT?

Or would I need to bring the MOT up and above the height of the top of the blocks running up the middle? To give a solid 50mm or so of MOT only at the surface level.